[0001] The present invention relates to medical anesthesia delivery systems for providing
breathing gases and anesthesia to a patient. Specifically, the invention relates to
an anesthesia system for delivering a breathing gas containing a settable anesthetic
concentration to a patient.
[0002] Fundamentally, anesthesia machines are used during surgery by clinicians to deliver
medical gases and inhaled anesthetic agent. Inspired breathing gases typically consist
of a mixture of oxygen, nitrous oxide and other gases. The oxygen is supplemented
to the patient to elevate the oxygen concentration above its concentration in air
to provide a safe margin of inspired oxygen therapy. The anesthetic agent is added
to the supply of breathing gases to provide the appropriate level of anesthesia so
that the patient remains unconscious, sedated and relaxed during the surgical procedure.
The inhaled anesthetic also provides amnesia of the surgical event.
[0003] It is common during the administration of anesthesia, for the patient to be connected
to a partial rebreathing circuit, for example a circle breathing system. With such
circuits, the patient's expired gases are recirculated, the CO
2 in the exhaled gases scrubbed, and the resulting gases are replenished with fresh
gas and again administered to the patient during inspiration.
[0004] A common technique used in anesthesia today is referred to as low flow anesthesia
where a minimal amount of fresh gas is added to the system. The technique enhances
warming and humidification of the gases in the patient circuit since less colder and
dry fresh gas is added and, of course, there is a savings in the cost of the anesthetic
agent since that agent is recirculated rather that being vented from the system to
a scavenging system or the like.
[0005] Generally, fresh gas flows in the range of 0.5 liters per minute can be used, although
low flow may be up to around three liters per minute. Basically, the fresh gas flow
is less than the patients minute volume so that there is partial rebreathing and the
lower the fresh gas flow, the more rebreathing occurs. Due to the recirculation gases,
however, the actual anesthetic concentration set by the user to be delivered by the
vaporizer as well as the oxygen concentration is different than the inspired anesthetic
and oxygen concentrations since the gases circulating in the patient circuit, in effect,
dilute the concentrations of the agent and the oxygen delivered in the fresh gas stream.
[0006] High flow anesthesia, on the other hand, may be in the order of providing fresh gas
into the system at the rate of three liters per minute and above and less gas is recirculated
from the patient's exhalation back through the system. The fresh gas flow approximates
or exceeds the patient's minute volume such that the exhaled gases are vented out
of the system. Typical high flows without gas recirculation occurs above 1.1 times
the patient's minute volume and, as indicated, result in a higher usage of anesthetic
agent as well as a loss of heat and humidification in the patient circuit.
[0007] In the anesthesia machines generally in use today, the gas and vapor delivery is
mechanically actuated by the clinician who adjusts the desired flow of oxygen out
to a common gas outlet. At high flow rates, where most of the inspired concentrations
to the patient are from the fresh gas, the ratio of the flow settings approximates
the delivery of inspired gases. Thus, at these high flows, the clinician can manually
set the various flow settings to obtain the concentrations of gas and vapor delivered
to the patient. As indicated, however, the use of high flow rates is wasteful of anesthetic
agent etc. as most of the agent laden gas is vented from the anesthesia machine.
[0008] The move to low flow anesthesia, while beneficial from an efficiency standpoint,
is, however, tedious for the clinician to carry out manual adjustments of flow to
achieve the targeted inspired concentration to the patient.
[0009] Accordingly, a new generation of anesthesia machines has emerged to facilitate very
low to closed circuit anesthesia. Examples of these new low flow anesthesia machines
are the Physioflex machine by Physio, Inc. and the machine described in U.S. Patent
5,094,235 of Westenskow. With these newer machines, the user sets the oxygen concentration
and either the inspired or expired anesthetic agent concentration to be delivered
to the patient instead of setting fresh gas flow rate of agent vapor concentration
delivered out of a common gas outlet. The machines use electronically controlled valves
to blend the gas mixture and an electronically controlled vaporizer to deliver the
anesthetic vapor. These electronic devices are controlled by a central processing
unit to achieve the precise control needed at the low flows.
[0010] A patient respiratory gas monitor located at the common Y-piece of the breathing
circuit senses and analyzes the oxygen concentration and the agent concentration in
the inspired and expired gases to and/or from the patient. Another agent and oxygen
monitor, collectively referred to as an inspiratory gas monitor, is used to monitor
the agent and oxygen concentrations of gases in the inspired limb of the patient circuit
and that measurement signal is fed to a CPU to close the control loops that actuate
the electronic gas mixer and the electronic anesthetic vaporizer to achieve the clinician's
desired delivery settings that are inputted to the CPU. The gas monitor in the Y-piece
can thus check the feedback from the gas monitor used in the automatic control scheme
and, preferably, the monitoring and feedback monitors are of differing technologies
to avoid unrecognizable common mode failures.
[0011] Thus it would be advantageous to quickly and accurately determine when the monitoring
and feedback monitors are malfunctioning totally or are simply out of calibration
so that proper and prompt corrective action can be taken.
[0012] As with all monitors, their measurements drift and change with different environmental
conditions. Differences in sensor technologies, location of measurements and processing
technique further exacerbate any mismatch in the measurements of the same parameters.
To overcome this, a bias correction can reduce the disagreement between these measurements.
Furthermore, if the monitored data are consistent but different from the user set,
it can be inferred that the delivery device failed to deliver the user set concentrations.
Accordingly, it would be advantageous to be able to carry out that procedure automatically.
Summary of the Invention
[0013] The present invention as defined in the accompanying claims makes use of two sets
of monitors for decting the concentration of a component; the concentrations measured
may be used to perform an on-line calibration of agent and oxygen monitors, compute
the feedback control bias and isolate a failure in the subsystem. Accordingly, the
aforesaid problems and difficulties with the present anesthesia machines may be alleviated
by the present invention.
[0014] The invention consists of an electronically actuated anesthesia gas machine that
is capable of delivering medical gases such as O
2, nitrous oxide and volatile anesthetic agent under the control of a central processing
unit (CPU). Examples of such electronically controlled gas mixers are mass flow controllers
commonly available in the process control industry. Several electronically actuated
anesthetic vaporizers are commercially available such as the Engstrom Elsa, of Gambro
Engstrom Company, Bromma, Sweden.
[0015] In carrying out the present invention, the patient may be ventilated by a ventilator
such as the Model 7900 ventilator of Ohmeda Inc. or by means of a manual breathing
bag manipulated by the clinician. As is common, the minute ventilation of the ventilation
is monitored, that is, the flow to the patient over a period of one minute. The patient
is connected to the ventilator and the fresh gas outlet by means of a circle type
breathing circuit although other breathing circuits may be employed as well as various
electronic gas mixers or electronic anesthetic vaporizers provided they can be remotely
controlled by a CPU.
[0016] As previously described with the new generation anesthesia machines, the clinician
can set the inspired oxygen concentration, the inspired or expired agent concentration
and the fresh gas flow rate. The actual carrying out of attaining the set values rests
with the CPU and its control of the various electronic gas mixing and agent vaporization
functions. An oxygen analyzer, for example an O
2 fuel cell type and an agent analyzer, for example the Model RGM5250 of Ohmeda Inc.
may be used to provide the feedback signal to the central processor unit to compare
against the user set inspired concentration. These sensors are located at the inspiratory
limb of the patient breathing circuit and will be collectively referred to as the
inspiratory gas monitor. An alternate analyzer that can carry out the monitoring of
both O
2 and agent concentrations in the patient circuit is the Rascal agent analyzer, also
marketed by Ohmeda Inc. and based on Raman spectroscopy.
[0017] In carrying out the administration of anesthesia with such machine, in the control
of the inspired oxygen or anesthetic agent, the difference between the measurement
values and the user set values are used to adjust the delivery of the gas mixer and
or electronic vaporizer to bring the inspired measured values to the concentrations
set by the user and inputted to the CPU.
[0018] Algorithms to perform these automatic feedback controls are well understood and an
example of such a control scheme is the PI control described in U.S. Patent 5,094,235.
The exact control strategy is not essential to this invention as long as the feedback
values of measured O
2 and agent concentrations are used to adjust, if necessary, the electronic mixer and/or
anesthetic vaporizer to match the values inputted by the clinician.
[0019] In closed circuit electronic gas delivery systems, the fresh gas flow rates are indirectly
controlled such that adequate gas flows are delivered to maintain the breathing circuit
volume and the gas and agent concentrations established by the clinician. The minimal
flow delivery systems fresh gas flow rates are adjusted to minimize the gases that
are exhausted from the breathing circuit.
[0020] As previously described, when the total fresh gas flow rate is low, more of the patient
expired gases are returned through the absorber to be rebreathed by the patient. While
this is desirable to save agent, the recirculated gases alter the composition of the
fresh gas delivered to the patient. However, during high fresh gas flow rates, at
open-circuit operations, excess gases are pushed through the absorber and relieved
through the ventilator bellows. No patient gases are recirculated and therefore only
the gases that are delivered by the electronic gas mixer and electronic agent vaporizer
flow into the inspiratory limb of the patient circuit. The same concentrations of
gases eventually also flow through the patient wye of the breathing circuit during
the inspiratory phase of ventilation. Furthermore, once the dynamics of the high flow
delivery settles, the composition of gases in the fresh gas lines and the inspiratory
limb of the breathing circuit are the same. Therefore, the O
2 and agent concentrations set to and delivered by the gas mixer and vaporizer can
be directly compared with the gas compositions measured at the inspired limb and the
gases during the inspiratory phase of the gases measured at the patient wye by the
respiratory gas monitor. This provides three sets of composition data relating to
the same gases flowing through the system that can be compared to carry out various
diagnoses and corrections to their inconsistencies.
[0021] The data with respect to composition at the three points can, therefore, at high
flows, be compared for a number of purposes. One can compare the data between any
of the corresponding parameters, i.e. O
2 concentration, and note the differences. If the data from two points compares favorable,
that is, within certain error limits, and the third is outside a certain limit, then
the device or monitor generating the errant data can be assumed to have failed and
the clinician alerted to that potential problem. If all three data points agree within
predetermined allowable limits, it can correspondingly be assumed that all of the
monitors and mixers/vaporizers are operating normally. In such case, a bias value
can be computed as the difference between the user monitored parameter and the feedback
control parameter. The bias can be used to offset the feedback control error, thus
matching the user set inspired gas delivery to the user monitored inspired measurement.
That bias can remain even when the flow is returned to the low flow condition and
can be readjusted (if desired) each time the flow is returned to a high flow delivery.
[0022] As a further use of the information available, if the two measurement data agree
to within a certain tolerance, for example, the sum of their individual error tolerances,
and a third (actuator) data differs from each of the first two data points by more
than its known tolerance, for example, the error of each of the measurement tolerances
but less than the combined tolerances, the sum of its measurement and each of the
first two measurements, then the third parameter may be improved by recalibrating
to the error tolerance weighted mean value of the first two data points. It also indicates
that it is not a total failure but simply needs recalibration or adjustment.
[0023] Mathematically, lets assume that X
1 and X
2 are the readings of the first two measurements, respectively. Furthermore, assume
that e
1 and e
2 are the known tolerances of the measurements X
1 and X
2, respectively.
[0024] If
Magnitude of |X
1 - X
2| < |e
1| + |e
2|
and Magnitude of |e
1| < |X
3 - X
1| < |e
1| + |e
3|
and Magnitude of |e
2| < |X
3 - X
2| < |e
2| + |e
3|
[0025] Then
X
3, corrected recalibration improvement to X
3 based on the error tolerance weighted mean value is as follows:
[0026] The above example by no means limit the method to compute the corrected recalibration
values. Other correction methods established in the field of statistics can similarly
be used to make the above correction.
[0027] In each of the foregoing data checks and recalibrations or adjustments, the need
exists, obviously, to carry out the gathering of data from the three points during
high flow. Such checks, therefore, may automatically be carried out during various
times during the anesthesia that high flow is initiated such as when speed of response
is needed to change a user set point or to rapidly refill the circuit gas volume following
a disconnected circuit. If the clinically prompted increase in fresh gas flow does
not occur for a long period, (the duration depends on the stability of the devices)
the anesthesia machine can initiate such an increase in total fresh gas flow rate
automatically at predetermined criteria, such as fixed intervals.
[0028] As can be seen, by increasing the fresh gas flow to high flow above the minute ventilation
condition, the delivery device setting (derived from the clinician input) and the
two pairs of gas measurements can be directly compared. In doing so, a failure in
the gas delivery system can be localized. Furthermore, the performance of the gas
delivery system can be retuned and therapy delivery can be matched to the clinician's
monitored parameter.
[0029] Other features of the present anesthesia system will become more apparent in light
of the following detailed description of a preferred embodiment thereof and as illustrated
in the accompanying drawings.
Brief Description of the Drawings
[0030] The Figure is a block diagram of an anesthesia system constructed in accordance with
the present invention.
Detailed Description of the Invention
[0031] Referring now to the Figure, there is shown a block diagram of an anesthesia system
adapted to carry out the subject invention. As shown, a ventilator 10 is provided
and which may be of the type shown and described in U.S. Patent 5,315,989 assigned
to the present applicant. That ventilator 10 of the aforementioned U.S. Patent has
an inhalation cycle and an exhalation cycle controlled by a central processing unit.
[0032] The ventilator 10 provides gas to the patient during the inhalation cycle via a conduit
12 to the patient breathing circuit 14 where it is delivered to the patient 16. The
ventilator 10 typically includes a bellows assembly 18 and air or other powering gas
is supplied to the bellows assembly 18 via conduit 15, exterior of the bellows 20
and which then collapses the bellows 20 to force gas within the bellows 20 to the
patient 16. As will be described herein, the embodiment includes a ventilator 10 and
bellows assembly 18, however, it will be understood that the present invention can
be employed to the situation where the patient is being "bagged" by the clinician
or is carrying out spontaneous breathing but is connected to the breathing circuit.
[0033] As also noted in the aforementioned U.S. Patent, the patient breathing circuit 14
itself conventionally includes an inspiratory limb 22 and an expiratory limb 24 and
the patient is connected to a wye connection 26 located intermediate the inspiratory
and the expiratory limbs 22,24. The means of connection may be an endotracheal tube,
face mask or other interface between the patient 16 and the patient breathing circuit
14.
[0034] In conventional operation, gas is delivered to the patient 16 by means of a powering
gas from ventilator 10 that collapses the bellows 20 to drive the gas into conduit
12 and then into the tee 28 where the gas enters a conduit 30 and passes through an
absorber 32. After passing through the absorber 32, the gas enters the inspiratory
limb 22 of the patient breathing circuit 14 to be administered to the patient 16.
As the patient exhales, that exhalation, now laden with CO
2, passes through the expiratory limb 24 where it again passes through the tee 28 and
continues to the absorber 32 where the CO
2 is eliminated by a CO
2 absorbing material, such as sodalime.
[0035] A pair of check valves 34 and 36 are positioned in the patient breathing circuit
14 in the expiratory and inspiratory limbs 24 and 22, respectively, to maintain the
flow of gas in the proper direction around the circle patient breathing circuit 14.
[0036] A flow of fresh gas is also introduced into the patient breathing circuit 14 and,
as shown, is added at a tee 38 and thus into the patient breathing circuit 14. That
flow of fresh gas is provided from a source of gas, typically oxygen and nitrous oxide
to aid in anesthetizing the patient. As shown in the Figure, there is a supply of
oxygen 40, nitrous oxide 42, air 44 and carbon dioxide 45 and such supply may be through
a central piping system of a hospital or may be through the use of individual cylinders
of such gases.
[0037] In any event, the gases are mixed in a gas mixer 46 in the proportion desired by
the user. The actual control of the proportions and the flow through the gas mixer
46 is controlled by a central processing unit (CPU) 48 as will be described. The mixed
gas from the gas mixer 46 then passes through an agent vaporizer 50 where liquid anesthetic
agent is vaporized and added to the stream of gas such that anesthetic laden gas continues
into a conduit 52 and enters the patient breathing circuit 14 at the tee 38.
[0038] The control of the agent vaporizer 50 is by means of the CPU 48 and which determines
the percentage concentration of anesthetic agent that is in the gas that enters the
patient breathing circuit 14 and thus that is supplied to the patient 16 to induce
and maintain anesthesia.
[0039] The CPU 48 is, in turn, controlled by a mixer setting device or user input 54 provided
so that the clinician can input the data needed to determine the various parameters
to provide the gas flow and anesthetic concentration desired to anesthetize the patient.
[0040] In the overall flow scheme of the present conventional system is therefore such that
the gas in the bellows 20 is forced by the ventilator 10 into conduit 12 in accordance
with the arrows A during the inhalation cycle of the patient 16. The gas thus passes
through the tee 28 and through absorber 32 where it further passes through tee 38
and into the inspiratory limb 22 of the patient breathing circuit 14. At tee 38, fresh
gas containing a predetermined concentration of an anesthetic agent is joined with
the gas from the bellows 20 and proceeds with the gases already circulating in patient
breathing circuit 14 and administered to the patient 16.
[0041] When the patient exhales, the exhaled gas passes through the expiratory limb 24 of
the patient breathing circuit 14 through tee 28 and continue through the conduit 12
and into the bellows 20. At the same time, fresh gas that continuously flows into
the circuit 14 from conduit 52 is also directed towards the bellows 20 after passing
through the patient breathing circuit 14. When the bellows 20 reaches the end of its
travel, any excess gas is popped off from the bellows 20 via pop-off valve 58 and
exits the system via conduit 59.
[0042] During the inspiratory phase, the bellows 20 is driven downwardly by the ventilator
10. The unidirectional check valves 34 and 36 direct the gas from the bellows 20 to
conduit 12 and through the absorber 32 where the gas is scrubbed of CO
2. Also directed is the fresh gas from conduit 52 towards the patient 16 via limb 22
of breathing circuit 14.
[0043] As can be seen, therefore, the anesthesia system is basically a circle system where
the gas continues to pass in a circle as shown by the arrows B with the addition of
fresh gas and the anesthetic agent added to that gas in the direction of Arrow C as
the gas passes around the circle.
[0044] As a further component of the overall anesthesia system, an inspiratory gas monitor
60 is provided to detect certain gases entering into the inspiratory limb 22 and thus
analyze the fresh gas added in conduit 52 carrying gas from the mixer 46 and to which
an amount of anesthetic agent has been added by agent analyzer 50. A typical O
2 analyzer may be a oxygen fuel cell and an agent analyzer may be an RGM 5250 commercially
marketed by Ohmeda Inc.
[0045] The O
2 and agent inspired measurements of the inspiratory gas monitor 60 are provided to
CPU 48 to compute the rate of gas flows and anesthetic vapor delivered by the gas
mixer 46 and vaporizer 50, respectively, to maintain the user delivered inspired concentration
set by the input 54. The feedback control algorithm to meet the user desired setting
is secondary to this invention.
[0046] A further monitor, a respiratory gas monitor 56 is also provided in the system and
is located in the patient wye 26 and thus can monitor the actual gases that are either
the inspired or expired gases of the patient 16. A typical analyzer for such user
may be, again, the Ohmeda Inc. RGM analyzer or the Rascal gas analyzer, also commercially
available from Ohmeda Inc. The inspiratory gas monitor 56 may also analyze the concentration
of CO
2 and nitrous oxide that can reach the patient 16. That CO
2 and nitrous analysis is thus provided to the CPU 48.
[0047] An alarm 62 is also provided as controlled by the CPU 48, the purpose of which will
be later explained.
[0048] As can now be seen, the overall anesthesia system is controlled by the CPU 48 based
on feedback from the inspiratory gas monitor 60 in a feed back loop to achieve the
agent and gas mixing concentrations set by the clinician with the user input 54 to
CPU 48. The anesthesia system can thus operate at low flows since the overall control
is CPU controlled and the clinician does not have to carry out the tedious titration
of gases at the low flows. As also noted, at low flow, the concentrations are strongly
influenced by the recirculation of the patients exhalation and therefore the composition
of gases and vapor delivered out of the fresh gas line is different from the concentrations
at the inspiratory gas monitor 60 and the respiratory gas monitor 56. However, at
high flows greater than minute ventilation the composition of the fresh gas added
to the system and analyzed by the inspiratory gas monitor 60 will be the same as the
respiratory gas administered to the patient at the patient wye 26 and analyzed by
the respiratory gas monitor 56.
[0049] As indicated, low flow is characteristic of a flow of about one liter per minute
or less of fresh gas and, the lower the flow of fresh gas, certainly, the more rebreathing
occurs in the system.
[0050] With high flow through the anesthesia system greater than the minute volume of the
patient, say about 1.1 times, almost no rebreathing occurs. All of the exhaled gas
is vented through the pop-off valve 58 and out through the conduit 59 which may be
connected to a scavenging system to rid the surrounding atmosphere of the anesthetic
laden gases. The minute ventilation is basically the amount of gas delivered to the
patient in a minute and, in the aforedescribed case where a ventilator is used, the
value of minute ventilation is normally provided as a setting on the ventilator or
a reading from the ventilator control panel. The minute ventilation may, however,
readily be determined from standard monitors in the cases where a ventilator is not
used, such as when the clinician is actually ventilating the patient by manipulating
a bag, i.e. bagging the patient, or where the patient is spontaneously breathing the
gas through his own effort from the patient breathing circuit. In the case of the
bagging situation or spontaneous breathing, the minute ventilation is readily determined
by ascertaining the tidal volume, that is, the volume of gases inspired by the patient,
and the breaths per minute. Such measurements are generally available to the clinician
and thus, the minute ventilation is derived by multiplying the tidal volume in liters
per breath by the breaths per minute to arrive at liters per minute.
[0051] Accordingly, the through flows, the gas compositions and vapor compositions through
the patient breathing circuit 14 are the same and thus, both the inspiratory gas monitor
60 that is in the feedback loop to the CPU 48 and the respiratory gas monitor 56 should,
during inspiration, read the same parameter values of gas composition and vapor concentration.
Thus, two sets of measured data are available to the CPU 48 and should be consistent.
There is also a set of data available from the user input 54 and, at high flows in
the open circuit operations, are used to command the gas and agent composition in
the fresh gas and therefore there are three sets of data that could bear some correlation,
that is, if the system is operating correctly, the delivered gas and vapor concentration
as set to the mixer and vaporizer should match the data of those compositions from
the inspiratory gas monitor 60 as well as the inspired measurements of the respiratory
gas monitor 56.
[0052] It should be noted that such correlation of the three sets of data will only occur
at the high flows, therefore the system hereinafter described will be usable at start-up
of the anesthesia system where a high flow is initiated, during the clinical operation
where a high flow is initiated in order, for example, to make a rapid change in the
gas or vapor concentrations, or upon depletion of the gas from the circuit and the
machine is refilling the system or, alternatively the anesthesia system may periodically,
on some predetermined timed cycle, simply switch into a high flow mode and carry out
the system analysis and checks of the present invention.
[0053] Given the three sets of data, the CPU can now carry out various safety checks and
analysis to detect and locate a fault and also to make certain corrections to the
overall anesthesia system
[0054] In one embodiment, the CPU, by a comparator, compares the various values of the oxygen
concentration and the anesthetic vapor concentration that is set to the mixer and
vaporizer, available from the inspiratory gas monitor 60 and the respiratory gas monitor
56 and compares the various sets of data. Thus, if all of the separate sets of data
agree, it can be assumed that the system is operating properly. In such case, a bias
value may be calculated by the CPU as a difference between the user monitored parameter
and the feedback control parameter. The bias, so delivered, can be used to offset
the feedback control error, thus better matching the user set inspired gas delivery
to the user monitored inspired measurement. The bias, once determined, remains in
the control algorithm even after the fresh gas is reduced back to low flow conditions.
[0055] If, on the other hand, two sets of data are within certain limits and the third set
of data is outside a predetermined limit, it is assumed that the third set of data,
either gas or agent delivered device, the respiratory gas monitor 56 or the inspiratory
gas monitor 60 is in error and a error message or alarm can be activated in the alarm
62.
[0056] As a further use of the three sets of information available within the CPU 48, if
the two measurement data agree to within a certain tolerance, for example, the sum
of their individual error tolerances, and a third (actuator) data differs from each
of the first two data points by more than a predefined tolerance, for example, the
error of each of the measurements tolerances but less thant a combined tolerance,
for example, the sum of its measurement and each of the first two measurements, then
the third parameter may be improved by recalibrating to the error tolerance weighted
mean value of the first two data points.
1. . An anesthesia system for delivering a breathing gas containing a settable anesthetic
concentration to a patient, said anesthesia system comprising: a patient circuit (14)
for administering the breathing gas and anesthetic agent to the patient, said patient
circuit having a wye connector (26) for connection to a patient through which inhaled
and exhaled gases pass to and from a patient, a fresh gas supply (46,50) providing
fresh gas to said patient circuit (14), said fresh gas supply comprising an electronic
controlled gas mixer (46) for providing a mixture of gases at a settable proportion
and an electronic controlled vaporizer (50) for introducing anesthetic vapor to the
mixture of gases from said electronic controlled gas mixer, a CPU (48) controlling
said electronic controlled vaporizer (50) and said electronic controlled mixer (46),
a mixer setting device (54) operable by a user to input to said CPU the concentration
of at least one component of the breathing gas desired to be administered to a patient
through said patient circuit (14), a first gas monitor (56) for analyzing said at
least one component and means to cause a flow of gas to enter said patient circuit
(14) from said fresh gas supply (46,50),
the first gas monitor (56) is arranged for analyzing said at least one component at
or near said wye connector (26), the means to cause a flow of gas to enter said patient
circuit (14) from said fresh gas supply (46,50) is such as to cause a high flow of
gas to enter the patient circuit (14), characterized in that the system includes a second gas monitor (60) detecting the concentration of said
at least one component in the gas circulating within said patient circuit (14), and
said CPU (48) includes means to compare the concentration of said at least one component
determined by said first gas monitor (56), said second gas monitor (60) and the concentration
of said at least one component inputted by a user with said input device (54) when
said high flow of gas is entering said patient circuit.
2. An anesthesia system as defined in Claim 1 wherein said at least one component is
or includes oxygen.
3. An anesthesia system as defined in Claim 1 or in claim 2 wherein said at least one
component is or includes anesthetic vapor.
4. An anesthesia system as defined in Claim 2 or in Claim 3 wherein said CPU (48) determines
a fault condition when the concentration of said at least one component determined
from said first gas monitor (56) and said second gas monitor (60), and said concentration
of said at least one component inputted by a user to said mixer setting device (54)
and delivered by the system are compared and are not within predetermined limits with
respect to each other.
5. An anesthesia system for delivering a breathing gas containing a settable anesthetic
concentration to a patient as defined in Claim 4, wherein said component is oxygen
and/or the anesthetic agent.
6. An anesthesia system as defined in any one of Claims 1 to 5 wherein said means to
cause a high flow of gas to enter said patient circuit includes a timer that activates
said means at predetermined intervals.
7. An anesthesia system as defined in any one of Claims 1 to 5 wherein said means to
cause a high flow of gas to enter said patient circuit comprises a manual activator
operable by a user.
8. An anesthesia system for delivering a breathing gas containing a settable anesthetic
concentration to a patient as defined in any one of Claims 1 to 7 wherein said CPU
(48) provides a bias signal to correct the reading of at least one of said first and
second gas monitors (56,60) and said bias signal is determined by said CPU comparing
said values of said at least one component concentration from said first and second
gas monitors.
9. An anesthesia system for delivering a breathing gas containing a known anesthetic
concentration to a patient as defined in any one of Claim 1 to 8 wherein said system
provides the fresh gas at a minute ventilation rate and said means to cause a high
flow of gas to enter said patient circuit is such that it increases the flow of said
fresh gas to be greater than the minute volume.
10. An anesthesia system as defined in Claim 8 wherein said first and second monitors
(56,60) are controlled by said bias signal from said CPU (48) and said CPU further
modifies said bias signal to one of said first and second monitors (56,60) based on
the comparison of said comparator.
11. An anesthesia system as defined in any one of claims 1 to 10 wherein said comparison
means provides a signal when one of said first or second monitors (56,60) or said
mixer setting device provides concentrations of said at least one component outside
a predetermined range with respect to the other two concentrations, said anesthesia
system further including an alarm (62) operable by said signal notifying the user
as to which device providing such concentrations is outside said predetermined limit.
1. Ein Anästheslesystem zur Lieferung eines Atemgases, das eine einstellbare Anästhetikumkonzentration
hat, an einen Patienten, wobei das genannte Anästhesiesystem enthält: einen Patientenkreislauf
(14) zur Verabreichung des Atemgases und des Anästhesiemittels an den Patienten, wobei
der genannte Patientenkreislauf einen Y-Verbinder (26) aufweist zur Verbindung mit
einem Patienten, durch den eingeatmete und ausgeatmete Gase zu und von einem Patienten
hindurchtreten, einer Frischgasversorgung (46, 50), die frisches Gas an den genannten
Patientenkreislauf (40) liefert, wobei die genannte Frischgasversorgung einen elektronisch
gesteuerten Gasmischer (46) enthält, um eine Mischung von Gasen vorzusehen In einem
einstellbaren Verhältnis und einen elektronisch gesteuerten Verdampfer (60) zum Einführen
von Anästhetikumdampf zu der Mischung von Gasen aus dem genannten elektronisch gesteuerten
Gasmischer, eine CPU (48), die den genannte elektronisch gesteuerten Verdampfer (50)
und den genannten elektronisch gesteuerten Mischer (46) steuert, einer Mischereinstellvorrichtung
(54), die betätigbar ist durch einen Benutzer, um der genannten CPU die Konzentration
von wenigstens einer Komponente des Atemgases einzugeben, die einem Patienten durch
den genannten Patientenkreislauf (14) zugeführt werden soll, einen ersten Gasmonitor
(56) zur Analysierung der genannten wenigstens einen Komponente und Mittel, um eine
Strömung von Gas zu bewirken in den genannten Patientenkreislauf (14) von der genannten
Frischgasversorgung (46, 50) einzutreten, wobei der erste Gasmonitor (56) angeordnet
ist zur Analysierung der genannten wenigstens einen Komponente bei oder nahe zu dem
genannten Y-Verbinder (26), wobei das Mittel um die Strömung von Gas zu bewirken In
den genannten Patientenkreislauf (14) von der genannten Frischgasversorgung (46, 50)
einzutreten so ist, dass eine hohe Strömung von Gas bewirkt wird in den Patientenkreislauf
(14) einzutreten.
dadurch gekennzeichnet,
dass das System einen zweiten Gasmonitor (60) einschließt, der die Konzentration der genannten
wenigstens einen Komponente in dem Gas detektlert, das innerhalb des Patientenkreislaufes
(14) zirkuliert, und dass die genannte CPU (48) Mittel umfasst, um die Konzentration
zu vergleichen der genannten wenigstens einen Komponente, die durch den genannten
ersten Gasmonitor (56) ermittelt wird, den genannten zweiten Gasmonitor (60) und die
Konzentration der genannten wenigstens einen Komponente, die durch einen Benutzer
mit der genannten Eingabevorrichtung (64) eingegeben wurde, wenn die genannte hohe
Strömung von Gas in den genannten Patientenkreislauf eintritt.
2. Ein Anästhesiesystem gemäß Anspruch 1,
wobei die genannte wenigstens eine Komponente Sauerstoff ist oder enthält
3. Ein Anästhesiesystem gemäß Anspruch 1 oder Anspruch 2,
wobei die genannte wenigstens eine Komponente Anästhetikumdampf ist oder enthält.
4. Ein Anästhesiesystem gemäß Anspruch 2 oder Anspruch 3,
wobei die genannte CPU (48) einen Fehlerzustand feststellt, wenn die Konzentration
der genannten wenigstens einen Komponente, die von dem genannten ersten Gasmonitor
(56) und dem genannten zweiten Gasmonitor (60) festgestellt wurde, und die genannte
Konzentration der genannten wenigstens einen Komponente, die durch einen Benutzer
in die genannte Mischerstelleinrichtung (54) eingegeben wurde und durch das System
geliefert wurde, verglichen werden und nicht Innerhalb vorgegebener Grenzen zueinander
sind.
5. Ein Anästhesiesystem zur Lieferung eines Atemgases, das eine einstellbare Anästhetikumkonzentration
an einen Patienten liefert gemäß Anspruch 4,
wobei die genannte Komponente Sauerstoff oder Anästhetikummittel ist.
6. Ein Anästhesiesystem gemäß einem der Ansprüche 1 bis 6,
wobei die genannten Mittel, die eine hohe Strömung von Gas bewirken, in den genannten
Patientenkreislauf einzutreten, einen Timer umfasst, der die genannten Mittel in vorbestimmten
Intervallen aktiviert.
7. Ein Anästhesiesystem gemäß einem der Ansprüche 1 bis 5,
wobei die genannten Mittel. die eine hohe Strömung von Gas bewirken, in den genannten
Patientenkrelslauf einzutreten, einen manuellen Aktivator enthält, der durch einen
Benutzer betätigbar ist.
8. Ein Anästheslesystem zur Lieferung eines Atemgases, das eine einstellbare Anästhetikumkonzeniration
enthält, an einen Patienten gemäß einem der Ansprüche 1 bis 7,
wobei die genannte CPU (48) ein Vorsignal liefert zur Korrektur der Messergebnisse
von wenigstes einem der ersten und zweiten Gasmonitore (56, 60) und wobei das genannte
Vorsignal bestimmt wird durch die genannte CPU, die die genannten Werte der genannten
wenigstens einen Komponentenkonzentration vergleicht von den genannten ersten und
zweiten Gasmonitoren.
9. Ein Anästheslesystem zur Lieferung eines Atemgases, das eine bekannte Anästhetikumkonzentration
an einen Patienten liefert gemäß einem der Ansprüche 1 bis 8.
wobei das genannte System das frische Gas in einer sehr kleinen Beatmungsrate vorsieht
und die genannten Mittel, die einen hohen Gasstrorn bewirken in den genannten Patientenkreislauf
einzutreten so sind, dass sie die Strömung des genannten frischen Gases erhöhen, so
dass sie größer ist als das sehr kleine Volumen.
10. Ein Anästhesiesystem gemäß Anspruch 8,
wobei die genannten ersten und zweiten Monitore (66, 60) gesteuert werden durch die
genannten Vorsignale der genannten CPU (46) und wobei die genannte CPU weiterhin das
genannte Vorsignal zu einem der genannten ersten und zweiten Monitore (56, 60) modifiziert
basierend auf dem Vergleich des genannten Komparators.
11. Ein Anästhesiesystem gemäß einem der Ansprüche 1 bis 10,
wobei die genannten Vergleichsmittel ein Signal liefern, wenn einer der genannten
ersten oder zweiten Monitore (56, 60) oder die genannte Mischerstellvorrichtung Konzentrationen
vorsehen der wenigstens einen Komponente außerhalb eines vorbestimmten Bereiches mit
Bezug auf die anderen zwei Konzentrationen, wobei das genannte Anästhesiesystem weiterhin
einen Alarm (62) enthält, der betätigbar ist durch das genannte Signal, um den Benutzer
zu informieren, welche Vorrichtung, die solche Konzentrationen liefert, außerhalb
der vorbestimmten Grenzen ist.
1. Système d'anesthésie pour délivrer, à un patient, un gaz respiratoire contenant une
concentration réglable en anesthésique, ledit système d'anesthésie comprenant : un
circuit de patient (14) pour administrer le gaz respiratoire et l'agent anesthésique
au patient, ledit circuit de patient ayant un connecteur en Y (26) pour la connexion
à un patient et au travers duquel passent, vers et depuis un patient, des gaz inhalés
et exhalés, une alimentation en gaz frais (46,50) fournissant du gaz frais audit circuit
de patient (14), ladite alimentation en gaz frais comprenant un mélangeur de gaz commandé
électroniquement (46) pour fournir un mélange de gaz selon une proportion réglable
et un vaporisateur commandé électroniquement (50) pour introduire de la vapeur anesthésique
dans le mélange de gaz provenant dudit mélangeur de gaz commandé électroniquement,
une unité centrale ou CPU (48) commandant ledit vaporisateur commandé électroniquement
(50) et ledit mélangeur commandé électroniquement (46), un dispositif de réglage (54)
du mélangeur actionnable par un utilisateur pour entrer, dans ladite CPU, la concentration
de l'un au moins des composants du gaz respiratoire que l'on désire administrer à
un patient via ledit circuit de patient (14), un premier contrôleur de gaz (56) pour
analyser ledit au moins un composant et un moyen pour provoquer l'entrée d'un flux
de gaz dans ledit circuit de patient (14) depuis ladite alimentation en gaz frais
(46,50), le premier contrôleur de gaz (56) étant agencé pour analyser ledit au moins
un composant au niveau ou à proximité dudit connecteur en Y (26), le moyen adapté
à provoquer l'entrée d'un flux de gaz dans ledit circuit de patient (14) depuis ladite
alimentation en gaz frais (46,50) étant tel qu'il cause l'entrée d'un fort flux de
gaz dans le circuit de patient (14),
caractérisé en ce que le système inclut un second contrôleur de gaz (60) détectant la concentration dudit
au moins un composant dans le gaz circulant au sein dudit circuit de patient (14),
et ladite CPU (48) inclut un moyen de comparaison de la concentration dudit au moins
un composant déterminé par ledit premier contrôleur de gaz (56), ledit second contrôleur
de gaz (60) et la concentration dudit au moins un composant entré par un utilisateur
dans ledit dispositif d'entrée (54) lorsque ledit fort flux de gaz pénètre dans ledit
circuit de patient.
2. Système d'anesthésie selon la revendication 1, dans lequel ledit au moins un composant
est, ou inclut de, l'oxygène.
3. Système d'anesthésie selon la revendication 1 ou la revendication 2, dans lequel ledit
au moins un composant est, ou inclut, de la vapeur anesthésique.
4. Système d'anesthésie selon la revendication 2 ou la revendication 3, dans lequel ladite
CPU (48) détermine une situation d'erreur lorsque la concentration dudit au moins
un composant, déterminée à partir dudit premier contrôleur de gaz (56) et dudit second
contrôleur de gaz (60), et ladite concentration dudit un moins un composant entrée
par un utilisateur dans ledit dispositif de réglage (54) du mélangeur et fournie par
le système sont comparées et ne sont pas comprises dans les limites prédéterminées
l'une par rapport à l'autre.
5. Système d'anesthésie pour délivrer à un patient un gaz respiratoire contenant une
concentration réglable en anesthésique selon la revendication 4, dans lequel ledit
composant est l'oxygène et/ou l'agent anesthésique.
6. Système d'anesthésie selon l'une quelconque des revendications 1 à 5, dans lequel
ledit moyen adapté à provoquer l'entrée d'un fort flux de gaz dans ledit circuit de
patient inclut un séquenceur qui active ledit moyen à des intervalles prédéterminés.
7. Système d'anesthésie selon l'une quelconque des revendications 1 à 5, dans lequel
ledit moyen adapté à provoquer l'entrée d'un fort flux de gaz dans ledit circuit de
patient comprend un activateur manuel actionnable par un utilisateur.
8. Système d'anesthésie pour délivrer à un patient un gaz respiratoire contenant une
concentration réglable en anesthésique, tel que défini dans l'une quelconque des revendications
1 à 7, dans lequel ladite CPU (48) fournit un signal de polarisation pour corriger
la lecture de l'un au moins desdits premier et second contrôleurs de gaz (56,60),
et ledit signal de polarisation est déterminé par ladite CPU comparant lesdites valeurs
de ladite concentration d'au moins un composant à partir desdits premier et second
contrôleurs de gaz.
9. Système d'anesthésie pour délivrer à un patient un gaz respiratoire contenant une
concentration connue en anesthésique, tel que défini selon l'une quelconque des revendications
1 à 8, dans lequel ledit système fournit le gaz frais à un débit de ventilation infime
et ledit moyen adapté à provoquer l'entrée d'un fort flux de gaz dans ledit circuit
de patient est tel qu'il augmente le flux dudit gaz frais pour qu'il soit supérieur
audit volume infime.
10. Système d'anesthésie selon la revendication 8, dans lequel lesdits premier et second
contrôleurs (56,60) sont commandés par ledit signal de polarisation provenant de ladite
CPU (48) et ladite CPU modifie davantage ledit signal de polarisation vers l'un desdits
premier et second contrôleurs (56,60) sur la base de la comparaison dudit comparateur.
11. Système d'anesthésie selon l'une quelconque des revendications 1 à 10, dans lequel
ledit moyen de comparaison fournit un signal lorsque l'un desdits premier ou second
contrôleur (56,60) ou dudit dispositif de réglage du mélangeur fournit des concentrations
dudit au moins un composant à l'extérieur d'une gamme prédéterminée par rapport aux
deux autres concentrations, ledit système d'anesthésie comprenant en outre une alarme
(62) actionnable par ledit signal et indiquant à l'utilisateur quel est celui des
dispositifs qui fournit de telles concentrations hors de ladite limite prédéterminée.